1. Field of the Invention
The present invention relates in general to glass furnace monitoring methods and in particular to a method and apparatus for monitoring a glass furnace.
2. Description of the Prior Art
In a conventional glass furnace, a mixed batch of solid raw materials is fed into a furnace tank, wherein the temperature of the solid batch is raised to a point where it liquifies and forms into a viscous mass of molten glass. The molten glass is usually referred to simply as melt. In older fuel-fired furnaces, the temperature of the batch is raised by burning gas or oil over the glass, causing heat to be radiated into the batch. In newer electric boost furnaces, heat is generated within the pool of melt itself by passing an electric current therethrough in combination with the above-described gas jets. In either type of furnace, the solid pieces of batch float on the melt until they absorb sufficient heat to liquify.
Both electric boost and fuel-fired type furnaces can be continuous units. In a continuous furnace, the mixed batch of raw materials is fed into one end of the furnace as is required to maintain a desired level of melt within the tank. At the other end of the furnace, the melt flows through a throat formed in the bottom of the tank into a refiner. The refiner distributes the melt to the forehearths of one or more glassware forming machines. Between the doghouse and the throat, a plurality of bubblers can be formed in the bottom of the furnace tank. The bubblers introduce air bubbles within the melt which slowly rise to the surface thereof. The bubbles gently agitate the melt to ensure a thorough mixing of the raw batch materials and to provide a more constant temperature distribution therein.
In any automated glassware forming process, it is critical that the melt supplied to the glassware forming machine remain at a constant temperature. If, however, pieces of relatively cool batch material travel the length of the furnace tank toward the region near the throat before being liquified, significant problems may develop with the melt withdrawn from the furnace because of temperature fluctuations. Hence, it is desirable to monitor the amount and location of the batch present on the surface of the melt within the various regions of the furnace tank to ensure that the furnace and bubblers are operating properly.
Such monitoring is presently accomplished by positioning a video camera near a window formed in the throat end of the furnace tank such that the surface of the melt can be viewed therethrough. An operator watches a cathode ray tube display of the interior of the furnace to locate and estimate the amount of batch floating on the surface of the pool of melt. Such a method is very subjective, with estimates varying greatly from operator to operator. Furthermore, it is highly inefficient to require a furnace operator to constant watch the video display of the surface of the batch and melt mixture within the tank.
U.S. Pat. No. 3,020,033 to McCreanor et al. discloses an inspection and control system for detecting defects on the surface of a body. A photosensitive device such as a video camera is utilized to scan the image of a surface of a moving irradiant body along a fixed line, which line extends substantially perpendicular to the direction of movement of the body. The electron beam of the photosensitive device produces a video signal wherein a relatively long pulse is generated for each scan of the electron beam. Superimposed on the long pulse are positive or negative short pulses which arise when the electron beam scans over a defect, the width of each pulse being proportional to the width of the defect it represents. The defect pulses trigger an oscillator which feeds a high frequency oscillatory signal to a counter only during the successive durations of the short defect pulses. The counter produces an output voltage when the total number of oscillations exceeds a given amount, indicating that the total area of the detected defects exceeds a predetermined limit.
U.S. Pat. No. 2,803,161 to Summerhayes, Jr. discloses a surface roughness measuring method and device. Light from a light source is reflected from the surface of a rotating piece of material into a photosensitive device. The photosensitive device generates an alternating current electrical signal having variations which correspond to the varying intensity light reflected from the area of the material surface being inspected. A spectrum analysis of the alternating current signal can be performed to produce a frequency distribution curve relating the amplitude of the alternating current signal to the frequency components therein. Other electro-optical inspection systems are disclosed in U.S. Pat. Nos. 3,779,649 to Bertoya et al. and 3,966,332 to Knapp et al.